2 * Detect hard and soft lockups on a system
4 * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
6 * Note: Most of this code is borrowed heavily from the original softlockup
7 * detector, so thanks to Ingo for the initial implementation.
8 * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
9 * to those contributors as well.
12 #define pr_fmt(fmt) "NMI watchdog: " fmt
15 #include <linux/cpu.h>
16 #include <linux/nmi.h>
17 #include <linux/init.h>
18 #include <linux/module.h>
19 #include <linux/sysctl.h>
20 #include <linux/smpboot.h>
21 #include <linux/sched/rt.h>
22 #include <linux/tick.h>
24 #include <asm/irq_regs.h>
25 #include <linux/kvm_para.h>
26 #include <linux/perf_event.h>
27 #include <linux/kthread.h>
30 * The run state of the lockup detectors is controlled by the content of the
31 * 'watchdog_enabled' variable. Each lockup detector has its dedicated bit -
32 * bit 0 for the hard lockup detector and bit 1 for the soft lockup detector.
34 * 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled'
35 * are variables that are only used as an 'interface' between the parameters
36 * in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The
37 * 'watchdog_thresh' variable is handled differently because its value is not
38 * boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh'
41 #define NMI_WATCHDOG_ENABLED_BIT 0
42 #define SOFT_WATCHDOG_ENABLED_BIT 1
43 #define NMI_WATCHDOG_ENABLED (1 << NMI_WATCHDOG_ENABLED_BIT)
44 #define SOFT_WATCHDOG_ENABLED (1 << SOFT_WATCHDOG_ENABLED_BIT)
46 static DEFINE_MUTEX(watchdog_proc_mutex
);
48 #ifdef CONFIG_HARDLOCKUP_DETECTOR
49 static unsigned long __read_mostly watchdog_enabled
= SOFT_WATCHDOG_ENABLED
|NMI_WATCHDOG_ENABLED
;
51 static unsigned long __read_mostly watchdog_enabled
= SOFT_WATCHDOG_ENABLED
;
53 int __read_mostly nmi_watchdog_enabled
;
54 int __read_mostly soft_watchdog_enabled
;
55 int __read_mostly watchdog_user_enabled
;
56 int __read_mostly watchdog_thresh
= 10;
59 int __read_mostly sysctl_softlockup_all_cpu_backtrace
;
61 #define sysctl_softlockup_all_cpu_backtrace 0
63 static struct cpumask watchdog_cpumask __read_mostly
;
64 unsigned long *watchdog_cpumask_bits
= cpumask_bits(&watchdog_cpumask
);
66 /* Helper for online, unparked cpus. */
67 #define for_each_watchdog_cpu(cpu) \
68 for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
71 * The 'watchdog_running' variable is set to 1 when the watchdog threads
72 * are registered/started and is set to 0 when the watchdog threads are
73 * unregistered/stopped, so it is an indicator whether the threads exist.
75 static int __read_mostly watchdog_running
;
77 * If a subsystem has a need to deactivate the watchdog temporarily, it
78 * can use the suspend/resume interface to achieve this. The content of
79 * the 'watchdog_suspended' variable reflects this state. Existing threads
80 * are parked/unparked by the lockup_detector_{suspend|resume} functions
81 * (see comment blocks pertaining to those functions for further details).
83 * 'watchdog_suspended' also prevents threads from being registered/started
84 * or unregistered/stopped via parameters in /proc/sys/kernel, so the state
85 * of 'watchdog_running' cannot change while the watchdog is deactivated
86 * temporarily (see related code in 'proc' handlers).
88 static int __read_mostly watchdog_suspended
;
90 static u64 __read_mostly sample_period
;
92 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts
);
93 static DEFINE_PER_CPU(struct task_struct
*, softlockup_watchdog
);
94 static DEFINE_PER_CPU(struct hrtimer
, watchdog_hrtimer
);
95 static DEFINE_PER_CPU(bool, softlockup_touch_sync
);
96 static DEFINE_PER_CPU(bool, soft_watchdog_warn
);
97 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts
);
98 static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt
);
99 static DEFINE_PER_CPU(struct task_struct
*, softlockup_task_ptr_saved
);
100 #ifdef CONFIG_HARDLOCKUP_DETECTOR
101 static DEFINE_PER_CPU(bool, hard_watchdog_warn
);
102 static DEFINE_PER_CPU(bool, watchdog_nmi_touch
);
103 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts_saved
);
104 static DEFINE_PER_CPU(struct perf_event
*, watchdog_ev
);
106 static unsigned long soft_lockup_nmi_warn
;
110 * Should we panic when a soft-lockup or hard-lockup occurs:
112 #ifdef CONFIG_HARDLOCKUP_DETECTOR
113 static int hardlockup_panic
=
114 CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE
;
116 * We may not want to enable hard lockup detection by default in all cases,
117 * for example when running the kernel as a guest on a hypervisor. In these
118 * cases this function can be called to disable hard lockup detection. This
119 * function should only be executed once by the boot processor before the
120 * kernel command line parameters are parsed, because otherwise it is not
121 * possible to override this in hardlockup_panic_setup().
123 void hardlockup_detector_disable(void)
125 watchdog_enabled
&= ~NMI_WATCHDOG_ENABLED
;
128 static int __init
hardlockup_panic_setup(char *str
)
130 if (!strncmp(str
, "panic", 5))
131 hardlockup_panic
= 1;
132 else if (!strncmp(str
, "nopanic", 7))
133 hardlockup_panic
= 0;
134 else if (!strncmp(str
, "0", 1))
135 watchdog_enabled
&= ~NMI_WATCHDOG_ENABLED
;
136 else if (!strncmp(str
, "1", 1))
137 watchdog_enabled
|= NMI_WATCHDOG_ENABLED
;
140 __setup("nmi_watchdog=", hardlockup_panic_setup
);
143 unsigned int __read_mostly softlockup_panic
=
144 CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
;
146 static int __init
softlockup_panic_setup(char *str
)
148 softlockup_panic
= simple_strtoul(str
, NULL
, 0);
152 __setup("softlockup_panic=", softlockup_panic_setup
);
154 static int __init
nowatchdog_setup(char *str
)
156 watchdog_enabled
= 0;
159 __setup("nowatchdog", nowatchdog_setup
);
161 static int __init
nosoftlockup_setup(char *str
)
163 watchdog_enabled
&= ~SOFT_WATCHDOG_ENABLED
;
166 __setup("nosoftlockup", nosoftlockup_setup
);
169 static int __init
softlockup_all_cpu_backtrace_setup(char *str
)
171 sysctl_softlockup_all_cpu_backtrace
=
172 !!simple_strtol(str
, NULL
, 0);
175 __setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup
);
179 * Hard-lockup warnings should be triggered after just a few seconds. Soft-
180 * lockups can have false positives under extreme conditions. So we generally
181 * want a higher threshold for soft lockups than for hard lockups. So we couple
182 * the thresholds with a factor: we make the soft threshold twice the amount of
183 * time the hard threshold is.
185 static int get_softlockup_thresh(void)
187 return watchdog_thresh
* 2;
191 * Returns seconds, approximately. We don't need nanosecond
192 * resolution, and we don't need to waste time with a big divide when
195 static unsigned long get_timestamp(void)
197 return running_clock() >> 30LL; /* 2^30 ~= 10^9 */
200 static void set_sample_period(void)
203 * convert watchdog_thresh from seconds to ns
204 * the divide by 5 is to give hrtimer several chances (two
205 * or three with the current relation between the soft
206 * and hard thresholds) to increment before the
207 * hardlockup detector generates a warning
209 sample_period
= get_softlockup_thresh() * ((u64
)NSEC_PER_SEC
/ 5);
212 /* Commands for resetting the watchdog */
213 static void __touch_watchdog(void)
215 __this_cpu_write(watchdog_touch_ts
, get_timestamp());
218 void touch_softlockup_watchdog(void)
221 * Preemption can be enabled. It doesn't matter which CPU's timestamp
222 * gets zeroed here, so use the raw_ operation.
224 raw_cpu_write(watchdog_touch_ts
, 0);
226 EXPORT_SYMBOL(touch_softlockup_watchdog
);
228 void touch_all_softlockup_watchdogs(void)
233 * this is done lockless
234 * do we care if a 0 races with a timestamp?
235 * all it means is the softlock check starts one cycle later
237 for_each_watchdog_cpu(cpu
)
238 per_cpu(watchdog_touch_ts
, cpu
) = 0;
241 #ifdef CONFIG_HARDLOCKUP_DETECTOR
242 void touch_nmi_watchdog(void)
245 * Using __raw here because some code paths have
246 * preemption enabled. If preemption is enabled
247 * then interrupts should be enabled too, in which
248 * case we shouldn't have to worry about the watchdog
251 raw_cpu_write(watchdog_nmi_touch
, true);
252 touch_softlockup_watchdog();
254 EXPORT_SYMBOL(touch_nmi_watchdog
);
258 void touch_softlockup_watchdog_sync(void)
260 __this_cpu_write(softlockup_touch_sync
, true);
261 __this_cpu_write(watchdog_touch_ts
, 0);
264 #ifdef CONFIG_HARDLOCKUP_DETECTOR
265 /* watchdog detector functions */
266 static bool is_hardlockup(void)
268 unsigned long hrint
= __this_cpu_read(hrtimer_interrupts
);
270 if (__this_cpu_read(hrtimer_interrupts_saved
) == hrint
)
273 __this_cpu_write(hrtimer_interrupts_saved
, hrint
);
278 static int is_softlockup(unsigned long touch_ts
)
280 unsigned long now
= get_timestamp();
282 if (watchdog_enabled
& SOFT_WATCHDOG_ENABLED
) {
283 /* Warn about unreasonable delays. */
284 if (time_after(now
, touch_ts
+ get_softlockup_thresh()))
285 return now
- touch_ts
;
290 #ifdef CONFIG_HARDLOCKUP_DETECTOR
292 static struct perf_event_attr wd_hw_attr
= {
293 .type
= PERF_TYPE_HARDWARE
,
294 .config
= PERF_COUNT_HW_CPU_CYCLES
,
295 .size
= sizeof(struct perf_event_attr
),
300 /* Callback function for perf event subsystem */
301 static void watchdog_overflow_callback(struct perf_event
*event
,
302 struct perf_sample_data
*data
,
303 struct pt_regs
*regs
)
305 /* Ensure the watchdog never gets throttled */
306 event
->hw
.interrupts
= 0;
308 if (__this_cpu_read(watchdog_nmi_touch
) == true) {
309 __this_cpu_write(watchdog_nmi_touch
, false);
313 /* check for a hardlockup
314 * This is done by making sure our timer interrupt
315 * is incrementing. The timer interrupt should have
316 * fired multiple times before we overflow'd. If it hasn't
317 * then this is a good indication the cpu is stuck
319 if (is_hardlockup()) {
320 int this_cpu
= smp_processor_id();
322 /* only print hardlockups once */
323 if (__this_cpu_read(hard_watchdog_warn
) == true)
326 if (hardlockup_panic
)
327 panic("Watchdog detected hard LOCKUP on cpu %d",
330 WARN(1, "Watchdog detected hard LOCKUP on cpu %d",
333 __this_cpu_write(hard_watchdog_warn
, true);
337 __this_cpu_write(hard_watchdog_warn
, false);
340 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
342 static void watchdog_interrupt_count(void)
344 __this_cpu_inc(hrtimer_interrupts
);
347 static int watchdog_nmi_enable(unsigned int cpu
);
348 static void watchdog_nmi_disable(unsigned int cpu
);
350 static int watchdog_enable_all_cpus(void);
351 static void watchdog_disable_all_cpus(void);
353 /* watchdog kicker functions */
354 static enum hrtimer_restart
watchdog_timer_fn(struct hrtimer
*hrtimer
)
356 unsigned long touch_ts
= __this_cpu_read(watchdog_touch_ts
);
357 struct pt_regs
*regs
= get_irq_regs();
359 int softlockup_all_cpu_backtrace
= sysctl_softlockup_all_cpu_backtrace
;
361 /* kick the hardlockup detector */
362 watchdog_interrupt_count();
364 /* kick the softlockup detector */
365 wake_up_process(__this_cpu_read(softlockup_watchdog
));
368 hrtimer_forward_now(hrtimer
, ns_to_ktime(sample_period
));
371 if (unlikely(__this_cpu_read(softlockup_touch_sync
))) {
373 * If the time stamp was touched atomically
374 * make sure the scheduler tick is up to date.
376 __this_cpu_write(softlockup_touch_sync
, false);
380 /* Clear the guest paused flag on watchdog reset */
381 kvm_check_and_clear_guest_paused();
383 return HRTIMER_RESTART
;
386 /* check for a softlockup
387 * This is done by making sure a high priority task is
388 * being scheduled. The task touches the watchdog to
389 * indicate it is getting cpu time. If it hasn't then
390 * this is a good indication some task is hogging the cpu
392 duration
= is_softlockup(touch_ts
);
393 if (unlikely(duration
)) {
395 * If a virtual machine is stopped by the host it can look to
396 * the watchdog like a soft lockup, check to see if the host
397 * stopped the vm before we issue the warning
399 if (kvm_check_and_clear_guest_paused())
400 return HRTIMER_RESTART
;
403 if (__this_cpu_read(soft_watchdog_warn
) == true) {
405 * When multiple processes are causing softlockups the
406 * softlockup detector only warns on the first one
407 * because the code relies on a full quiet cycle to
408 * re-arm. The second process prevents the quiet cycle
409 * and never gets reported. Use task pointers to detect
412 if (__this_cpu_read(softlockup_task_ptr_saved
) !=
414 __this_cpu_write(soft_watchdog_warn
, false);
417 return HRTIMER_RESTART
;
420 if (softlockup_all_cpu_backtrace
) {
421 /* Prevent multiple soft-lockup reports if one cpu is already
422 * engaged in dumping cpu back traces
424 if (test_and_set_bit(0, &soft_lockup_nmi_warn
)) {
425 /* Someone else will report us. Let's give up */
426 __this_cpu_write(soft_watchdog_warn
, true);
427 return HRTIMER_RESTART
;
431 pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
432 smp_processor_id(), duration
,
433 current
->comm
, task_pid_nr(current
));
434 __this_cpu_write(softlockup_task_ptr_saved
, current
);
436 print_irqtrace_events(current
);
442 if (softlockup_all_cpu_backtrace
) {
443 /* Avoid generating two back traces for current
444 * given that one is already made above
446 trigger_allbutself_cpu_backtrace();
448 clear_bit(0, &soft_lockup_nmi_warn
);
449 /* Barrier to sync with other cpus */
450 smp_mb__after_atomic();
453 add_taint(TAINT_SOFTLOCKUP
, LOCKDEP_STILL_OK
);
454 if (softlockup_panic
)
455 panic("softlockup: hung tasks");
456 __this_cpu_write(soft_watchdog_warn
, true);
458 __this_cpu_write(soft_watchdog_warn
, false);
460 return HRTIMER_RESTART
;
463 static void watchdog_set_prio(unsigned int policy
, unsigned int prio
)
465 struct sched_param param
= { .sched_priority
= prio
};
467 sched_setscheduler(current
, policy
, ¶m
);
470 static void watchdog_enable(unsigned int cpu
)
472 struct hrtimer
*hrtimer
= raw_cpu_ptr(&watchdog_hrtimer
);
474 /* kick off the timer for the hardlockup detector */
475 hrtimer_init(hrtimer
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
476 hrtimer
->function
= watchdog_timer_fn
;
478 /* Enable the perf event */
479 watchdog_nmi_enable(cpu
);
481 /* done here because hrtimer_start can only pin to smp_processor_id() */
482 hrtimer_start(hrtimer
, ns_to_ktime(sample_period
),
483 HRTIMER_MODE_REL_PINNED
);
485 /* initialize timestamp */
486 watchdog_set_prio(SCHED_FIFO
, MAX_RT_PRIO
- 1);
490 static void watchdog_disable(unsigned int cpu
)
492 struct hrtimer
*hrtimer
= raw_cpu_ptr(&watchdog_hrtimer
);
494 watchdog_set_prio(SCHED_NORMAL
, 0);
495 hrtimer_cancel(hrtimer
);
496 /* disable the perf event */
497 watchdog_nmi_disable(cpu
);
500 static void watchdog_cleanup(unsigned int cpu
, bool online
)
502 watchdog_disable(cpu
);
505 static int watchdog_should_run(unsigned int cpu
)
507 return __this_cpu_read(hrtimer_interrupts
) !=
508 __this_cpu_read(soft_lockup_hrtimer_cnt
);
512 * The watchdog thread function - touches the timestamp.
514 * It only runs once every sample_period seconds (4 seconds by
515 * default) to reset the softlockup timestamp. If this gets delayed
516 * for more than 2*watchdog_thresh seconds then the debug-printout
517 * triggers in watchdog_timer_fn().
519 static void watchdog(unsigned int cpu
)
521 __this_cpu_write(soft_lockup_hrtimer_cnt
,
522 __this_cpu_read(hrtimer_interrupts
));
526 * watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
527 * failure path. Check for failures that can occur asynchronously -
528 * for example, when CPUs are on-lined - and shut down the hardware
529 * perf event on each CPU accordingly.
531 * The only non-obvious place this bit can be cleared is through
532 * watchdog_nmi_enable(), so a pr_info() is placed there. Placing a
533 * pr_info here would be too noisy as it would result in a message
534 * every few seconds if the hardlockup was disabled but the softlockup
537 if (!(watchdog_enabled
& NMI_WATCHDOG_ENABLED
))
538 watchdog_nmi_disable(cpu
);
541 #ifdef CONFIG_HARDLOCKUP_DETECTOR
543 * People like the simple clean cpu node info on boot.
544 * Reduce the watchdog noise by only printing messages
545 * that are different from what cpu0 displayed.
547 static unsigned long cpu0_err
;
549 static int watchdog_nmi_enable(unsigned int cpu
)
551 struct perf_event_attr
*wd_attr
;
552 struct perf_event
*event
= per_cpu(watchdog_ev
, cpu
);
554 /* nothing to do if the hard lockup detector is disabled */
555 if (!(watchdog_enabled
& NMI_WATCHDOG_ENABLED
))
558 /* is it already setup and enabled? */
559 if (event
&& event
->state
> PERF_EVENT_STATE_OFF
)
562 /* it is setup but not enabled */
566 wd_attr
= &wd_hw_attr
;
567 wd_attr
->sample_period
= hw_nmi_get_sample_period(watchdog_thresh
);
569 /* Try to register using hardware perf events */
570 event
= perf_event_create_kernel_counter(wd_attr
, cpu
, NULL
, watchdog_overflow_callback
, NULL
);
572 /* save cpu0 error for future comparision */
573 if (cpu
== 0 && IS_ERR(event
))
574 cpu0_err
= PTR_ERR(event
);
576 if (!IS_ERR(event
)) {
577 /* only print for cpu0 or different than cpu0 */
578 if (cpu
== 0 || cpu0_err
)
579 pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
584 * Disable the hard lockup detector if _any_ CPU fails to set up
585 * set up the hardware perf event. The watchdog() function checks
586 * the NMI_WATCHDOG_ENABLED bit periodically.
588 * The barriers are for syncing up watchdog_enabled across all the
589 * cpus, as clear_bit() does not use barriers.
591 smp_mb__before_atomic();
592 clear_bit(NMI_WATCHDOG_ENABLED_BIT
, &watchdog_enabled
);
593 smp_mb__after_atomic();
595 /* skip displaying the same error again */
596 if (cpu
> 0 && (PTR_ERR(event
) == cpu0_err
))
597 return PTR_ERR(event
);
599 /* vary the KERN level based on the returned errno */
600 if (PTR_ERR(event
) == -EOPNOTSUPP
)
601 pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu
);
602 else if (PTR_ERR(event
) == -ENOENT
)
603 pr_warn("disabled (cpu%i): hardware events not enabled\n",
606 pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
607 cpu
, PTR_ERR(event
));
609 pr_info("Shutting down hard lockup detector on all cpus\n");
611 return PTR_ERR(event
);
615 per_cpu(watchdog_ev
, cpu
) = event
;
617 perf_event_enable(per_cpu(watchdog_ev
, cpu
));
622 static void watchdog_nmi_disable(unsigned int cpu
)
624 struct perf_event
*event
= per_cpu(watchdog_ev
, cpu
);
627 perf_event_disable(event
);
628 per_cpu(watchdog_ev
, cpu
) = NULL
;
630 /* should be in cleanup, but blocks oprofile */
631 perf_event_release_kernel(event
);
634 /* watchdog_nmi_enable() expects this to be zero initially. */
640 static int watchdog_nmi_enable(unsigned int cpu
) { return 0; }
641 static void watchdog_nmi_disable(unsigned int cpu
) { return; }
642 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
644 static struct smp_hotplug_thread watchdog_threads
= {
645 .store
= &softlockup_watchdog
,
646 .thread_should_run
= watchdog_should_run
,
647 .thread_fn
= watchdog
,
648 .thread_comm
= "watchdog/%u",
649 .setup
= watchdog_enable
,
650 .cleanup
= watchdog_cleanup
,
651 .park
= watchdog_disable
,
652 .unpark
= watchdog_enable
,
656 * park all watchdog threads that are specified in 'watchdog_cpumask'
658 static int watchdog_park_threads(void)
663 for_each_watchdog_cpu(cpu
) {
664 ret
= kthread_park(per_cpu(softlockup_watchdog
, cpu
));
669 for_each_watchdog_cpu(cpu
)
670 kthread_unpark(per_cpu(softlockup_watchdog
, cpu
));
678 * unpark all watchdog threads that are specified in 'watchdog_cpumask'
680 static void watchdog_unpark_threads(void)
685 for_each_watchdog_cpu(cpu
)
686 kthread_unpark(per_cpu(softlockup_watchdog
, cpu
));
691 * Suspend the hard and soft lockup detector by parking the watchdog threads.
693 int lockup_detector_suspend(void)
697 mutex_lock(&watchdog_proc_mutex
);
699 * Multiple suspend requests can be active in parallel (counted by
700 * the 'watchdog_suspended' variable). If the watchdog threads are
701 * running, the first caller takes care that they will be parked.
702 * The state of 'watchdog_running' cannot change while a suspend
703 * request is active (see related code in 'proc' handlers).
705 if (watchdog_running
&& !watchdog_suspended
)
706 ret
= watchdog_park_threads();
709 watchdog_suspended
++;
711 mutex_unlock(&watchdog_proc_mutex
);
717 * Resume the hard and soft lockup detector by unparking the watchdog threads.
719 void lockup_detector_resume(void)
721 mutex_lock(&watchdog_proc_mutex
);
723 watchdog_suspended
--;
725 * The watchdog threads are unparked if they were previously running
726 * and if there is no more active suspend request.
728 if (watchdog_running
&& !watchdog_suspended
)
729 watchdog_unpark_threads();
731 mutex_unlock(&watchdog_proc_mutex
);
734 static void update_watchdog_all_cpus(void)
736 watchdog_park_threads();
737 watchdog_unpark_threads();
740 static int watchdog_enable_all_cpus(void)
744 if (!watchdog_running
) {
745 err
= smpboot_register_percpu_thread_cpumask(&watchdog_threads
,
748 pr_err("Failed to create watchdog threads, disabled\n");
750 watchdog_running
= 1;
753 * Enable/disable the lockup detectors or
754 * change the sample period 'on the fly'.
756 update_watchdog_all_cpus();
762 static void watchdog_disable_all_cpus(void)
764 if (watchdog_running
) {
765 watchdog_running
= 0;
766 smpboot_unregister_percpu_thread(&watchdog_threads
);
773 * Update the run state of the lockup detectors.
775 static int proc_watchdog_update(void)
780 * Watchdog threads won't be started if they are already active.
781 * The 'watchdog_running' variable in watchdog_*_all_cpus() takes
782 * care of this. If those threads are already active, the sample
783 * period will be updated and the lockup detectors will be enabled
784 * or disabled 'on the fly'.
786 if (watchdog_enabled
&& watchdog_thresh
)
787 err
= watchdog_enable_all_cpus();
789 watchdog_disable_all_cpus();
796 * common function for watchdog, nmi_watchdog and soft_watchdog parameter
798 * caller | table->data points to | 'which' contains the flag(s)
799 * -------------------|-----------------------|-----------------------------
800 * proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
801 * | | with SOFT_WATCHDOG_ENABLED
802 * -------------------|-----------------------|-----------------------------
803 * proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED
804 * -------------------|-----------------------|-----------------------------
805 * proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
807 static int proc_watchdog_common(int which
, struct ctl_table
*table
, int write
,
808 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
811 int *watchdog_param
= (int *)table
->data
;
813 mutex_lock(&watchdog_proc_mutex
);
815 if (watchdog_suspended
) {
816 /* no parameter changes allowed while watchdog is suspended */
822 * If the parameter is being read return the state of the corresponding
823 * bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
824 * run state of the lockup detectors.
827 *watchdog_param
= (watchdog_enabled
& which
) != 0;
828 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
830 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
835 * There is a race window between fetching the current value
836 * from 'watchdog_enabled' and storing the new value. During
837 * this race window, watchdog_nmi_enable() can sneak in and
838 * clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
839 * The 'cmpxchg' detects this race and the loop retries.
842 old
= watchdog_enabled
;
844 * If the parameter value is not zero set the
845 * corresponding bit(s), else clear it(them).
851 } while (cmpxchg(&watchdog_enabled
, old
, new) != old
);
854 * Update the run state of the lockup detectors.
855 * Restore 'watchdog_enabled' on failure.
857 err
= proc_watchdog_update();
859 watchdog_enabled
= old
;
862 mutex_unlock(&watchdog_proc_mutex
);
867 * /proc/sys/kernel/watchdog
869 int proc_watchdog(struct ctl_table
*table
, int write
,
870 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
872 return proc_watchdog_common(NMI_WATCHDOG_ENABLED
|SOFT_WATCHDOG_ENABLED
,
873 table
, write
, buffer
, lenp
, ppos
);
877 * /proc/sys/kernel/nmi_watchdog
879 int proc_nmi_watchdog(struct ctl_table
*table
, int write
,
880 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
882 return proc_watchdog_common(NMI_WATCHDOG_ENABLED
,
883 table
, write
, buffer
, lenp
, ppos
);
887 * /proc/sys/kernel/soft_watchdog
889 int proc_soft_watchdog(struct ctl_table
*table
, int write
,
890 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
892 return proc_watchdog_common(SOFT_WATCHDOG_ENABLED
,
893 table
, write
, buffer
, lenp
, ppos
);
897 * /proc/sys/kernel/watchdog_thresh
899 int proc_watchdog_thresh(struct ctl_table
*table
, int write
,
900 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
904 mutex_lock(&watchdog_proc_mutex
);
906 if (watchdog_suspended
) {
907 /* no parameter changes allowed while watchdog is suspended */
912 old
= ACCESS_ONCE(watchdog_thresh
);
913 err
= proc_dointvec_minmax(table
, write
, buffer
, lenp
, ppos
);
919 * Update the sample period. Restore on failure.
922 err
= proc_watchdog_update();
924 watchdog_thresh
= old
;
928 mutex_unlock(&watchdog_proc_mutex
);
933 * The cpumask is the mask of possible cpus that the watchdog can run
934 * on, not the mask of cpus it is actually running on. This allows the
935 * user to specify a mask that will include cpus that have not yet
936 * been brought online, if desired.
938 int proc_watchdog_cpumask(struct ctl_table
*table
, int write
,
939 void __user
*buffer
, size_t *lenp
, loff_t
*ppos
)
943 mutex_lock(&watchdog_proc_mutex
);
945 if (watchdog_suspended
) {
946 /* no parameter changes allowed while watchdog is suspended */
951 err
= proc_do_large_bitmap(table
, write
, buffer
, lenp
, ppos
);
953 /* Remove impossible cpus to keep sysctl output cleaner. */
954 cpumask_and(&watchdog_cpumask
, &watchdog_cpumask
,
957 if (watchdog_running
) {
959 * Failure would be due to being unable to allocate
960 * a temporary cpumask, so we are likely not in a
961 * position to do much else to make things better.
963 if (smpboot_update_cpumask_percpu_thread(
964 &watchdog_threads
, &watchdog_cpumask
) != 0)
965 pr_err("cpumask update failed\n");
969 mutex_unlock(&watchdog_proc_mutex
);
973 #endif /* CONFIG_SYSCTL */
975 void __init
lockup_detector_init(void)
979 #ifdef CONFIG_NO_HZ_FULL
980 if (tick_nohz_full_enabled()) {
981 pr_info("Disabling watchdog on nohz_full cores by default\n");
982 cpumask_copy(&watchdog_cpumask
, housekeeping_mask
);
984 cpumask_copy(&watchdog_cpumask
, cpu_possible_mask
);
986 cpumask_copy(&watchdog_cpumask
, cpu_possible_mask
);
989 if (watchdog_enabled
)
990 watchdog_enable_all_cpus();